First post! I was hoping that I can just find some answers lurking, but seems to me that my specific problem wasn't shared by anyone else.

So here it is...My SES light was one a few months ago when it was really cold, my car died after backing out of a parking spot and driving in 1st gear for about 30 yards. I turned the car back on and even tried to rev the car up to get the RPM up but right after I turn it on it would just lose power and just shut off. I had about 40 miles left on gas. I called my dad and he just brought some gas and filled it up a bit and I was able to go to the nearest gas station and fill up. After the fill up, no issues. That is...until my gas started running low again (100 miles left or so). Filled it up and all was good.

a few weeks later it started to rough idle no matter what and I brought it to a shop and the mechanic showed me the list of error codes which was just misfires on all 6 cylinders. They replaced my spark plugs saying that they were bad and after the test drive said that the light came back on...and the mechanic 'figured' it was another thing where he said it'd be like a $600 fix...I decided to drive off thinking if I should just sell the car. But in the end I decided to try and fix it myself so I can actually learn how a car works and so I can save some money.

I did a smoke test and there were no air leaks so i put everything back together and cleared the code and when i drove my car it was fine. But the SES light came back on but still no rough idling. After my gas was a little more than half empty it started to to shake pretty bad when idle and when i drive in first gear the RPM shoots up even when i'm braking with the clutch in of course.

My car has 245,000 miles on it...but it runs real well on the highway, just the rough idle...any ideas on what it could be if its not an air leak or the spark plugs?? Or if it's hard to pin point, what should I try to replace or fix first? Fuel filter?? I assume it might be REALLY dirty if it was never changed by the previous owner...

I second the fuel pump and fuel filter getting replaced, also maybe some good fuel injector/system cleaner of some sort? For the lean codes really check those intake boots to the throttle body or even the disa orange gasket is usually a pretty big culprit plus the crank case system hoses as well. At least when I had those po171/4 codes those were my solutions

I second the fuel pump and fuel filter getting replaced, also maybe some good fuel injector/system cleaner of some sort? For the lean codes really check those intake boots to the throttle body or even the disa orange gasket is usually a pretty big culprit plus the crank case system hoses as well. At least when I had those po171/4 codes those were my solutions

Thanks for the input, guys! sorry my reply is late. Just got back from vacation and was playing catch up.

Even if the fuel pump is working, should i replace it? I opened it up and drove around with the cover open, def heard it working the whole time.

Also, as stated above...when my car has 25% gas left it starts and the shuts off...so i've been putting gas when the tank is half empty, but today with a a full tank of gas the car was reallllll shaky so i revv'd it up slowly and then the rough idle goes away until i let go of the gas pedal. Then, i gave it some gas faster and then let go at about 3000RPMs and then it shut off...Def. a fuel filter/pump problem??

Fuel pumps in our cars last about 5000 hours. Mileage and/or age aren't really relevant. Yes, fuel pumps can "soft fail." When the pump is soft failing it still pumps gas but not at the proper pressure of 45psi. The reason why your car has running issues when the fuel level is low is the pump has to scavenge for fuel. Replace the pump with a Siemens/VDO pump from bmaparts. Buy a new pump o-ring, fuel filter and fuel pump relay. Also, you'll want to replace the three short pieces of rubber fuel injection hose and the six clamps at the filter.

I second Fuel pump and fuel filter. You are probably looking at less then $200 (depending on pump) and if you replace the second fuel pump as well (probably not needed). I would in addition is pull the injectors out at the same time, and have an injector shop clean and flow match the injectors if you can.

I second Fuel pump and fuel filter. You are probably looking at less then $200 (depending on pump) and if you replace the second fuel pump as well (probably not needed). I would in addition is pull the injectors out at the same time, and have an injector shop clean and flow match the injectors if you can.

Okay, seems like i'm gonna try to get the filter and pump replaced first maybe the relay too? Another question is, have you guys tried to change the fuel filter with the car just on rhinoramps?

That sounds like a better idea haha. So i just did a quick search on how to check my fuel pressure. I don't have a fancy OBDII reader so I guess I'm gonna have to get a pressure checker with a schrader valve and then connect it to my fuel rail and see if it stays at 50psi (3.5 bar) for about 10 - 15 mins and if its drops below 3.0 barr, then its a bad fuel pump/filter correct?

Okay. So when i turn my key to the 2nd click the pressure stays 0. Wheni turn my car on it reads about 50psi and when i turn off, the pressure goes down to 0 in about 3 seconds...what does this mean?? Im finding a lot of different answers online...

Okay. So when i turn my key to the 2nd click the pressure stays 0. Wheni turn my car on it reads about 50psi and when i turn off, the pressure goes down to 0 in about 3 seconds...what does this mean?? Im finding a lot of different answers online...

I haven't personally tested fuel pressure on our cars, however the rail should maintain pressure. This looks like a informative video, I skipped ahead almost 10 minutes to the fuel pressure testing.

I think the vac line for fuel pressure connects behind the intake manifold, and the regulator under the car next to the fuel filter (on my car). Along with the return line.

Okay. So when i turn my key to the 2nd click the pressure stays 0. Wheni turn my car on it reads about 50psi and when i turn off, the pressure goes down to 0 in about 3 seconds...what does this mean?? Im finding a lot of different answers online...

Every E46 should have a replacement fuel pump at this point. It is a very easy DIY, easier than changing a tire or the fuel filter. Your car is 15-16 years old at this point, if the pump is original, it NEEDS to be replaced.

A Siemens OE pump from OEMBimmerparts.com is like $135 on your doorstep.

I do not even bother checking fuel pressure in cars over 8-10 years old anymore, I just replace the fuel pump, they all need it. It is just a ticking time bomb that leaves the car stranded after is causes strange driveability problems before it hard fails.

If the pump does not resolve the pressure drop problem, then look further.

Every E46 should have a replacement fuel pump at this point. It is a very easy DIY, easier than changing a tire or the fuel filter. Your car is 15-16 years old at this point, if the pump is original, it NEEDS to be replaced.

A Siemens OE pump from OEMBimmerparts.com is like $135 on your doorstep.

I do not even bother checking fuel pressure in cars over 8-10 years old anymore, I just replace the fuel pump, they all need it. It is just a ticking time bomb that leaves the car stranded after is causes strange driveability problems before it hard fails.

If the pump does not resolve the pressure drop problem, then look further.

oh my goodness.......the links in your signature!!! PERFECT description of the condition i had back in winter! 25% gas left and it wouldn't start and it started when i put some more gas in! You sir, are a life saver. changing my filter and pump. hopefully, those are the reason for my codes and rough idling...THANKS!

a little update on my 'works'. Was able to get a new fuel filter on. Seems like the previous owner(s) never changed the filter since it was the BMW safety hose clamps and a BMW logo stamped fuel filter or maybe they got it serviced at the dealership? Regardless, the 10mm bolt that was also stuck on the filter holder was rusted the crap out of it that it took excessive force to take off the nut (it was raining rust from that thing haha)

I also just ordered 1/8in vacuum hose for the regulator because every auto store near me (even home depot) did not carry 1/8in. an autozone worker told me that my best bet was online since BMW has a patent or w.e and won't let auto shops sell their sizes? I don't remember exactly what he said.

Another question is, i left the cover off since i'll be going under the car in a few days anyways to replace the vacuum hose. Will it be okay to drive around without it for a few days?

Good news is that my rough idling stopped, but still ordered a new fuel pump since my car did die when it was 1/4 full and don't want that happening again.

And yes, i think it was clogged as hell. when i took off the old filter a good amount of gas was in it and would not drip down the front end even with me shaking it. the gas only dripped out the back end. Will update you guys after i install the new pump and vacuum hose after it gets here. Again, thanks for all your help!

Its okay to drive without the under cover, just not advised. I need to get mine back on...

You are replacing the secondary fuel pump, and the primary, right? If it dies below 1/4 tank.

Crazy about the vac line, never had problem getting basic black rubber! The real question is why they don't have any? Did someone buy it, all, from every store! Perhaps they knew you would need it... All we know for sure, is the validity of such conspiracy ;P

Its okay to drive without the under cover, just not advised. I need to get mine back on...

You are replacing the secondary fuel pump, and the primary, right? If it dies below 1/4 tank.

Crazy about the vac line, never had problem getting basic black rubber! The real question is why they don't have any? Did someone buy it, all, from every store! Perhaps they knew you would need it... All we know for sure, is the validity of such conspiracy ;P

I think my car has only one fuel pump? One in the back seat on the passenger side. That's what I'm seeing in the DIY videos on youtube. Dont see anything about the secondary pump...unless im missing something??

Btw...rough idle is back after the filter replacement..shut off on me when i started my car and was in the phone for like a minute. Doesnt rough idle when I immediately drive off though

The jet pump is responsible for moving the last 1/4 tank or so from the left too the right side of the fuel tank. So if you ever run out of gas at 1/4 tank, I suppose you should turn hard left ASAP to slosh as much fuel to the right before you loos speed... lol. I'm looking for more information, but cant seem to find much. Mostly main fuel pump information, and threads regarding the M3 specifically. I presume our cars do have this pump still, but could be wrong...? lol

I found a thread at one time where the person had adapted an M3 suction base in the tank to the standard E46. Apparently it has a larger volume for fuel reserve within the pickup.

Every E46 should have a replacement fuel pump at this point. It is a very easy DIY, easier than changing a tire or the fuel filter. Your car is 15-16 years old at this point, if the pump is original, it NEEDS to be replaced.

A Siemens OE pump from OEMBimmerparts.com is like $135 on your doorstep.

I do not even bother checking fuel pressure in cars over 8-10 years old anymore, I just replace the fuel pump, they all need it. It is just a ticking time bomb that leaves the car stranded after is causes strange driveability problems before it hard fails.

If the pump does not resolve the pressure drop problem, then look further.

So i replaced the filter and pump and from a cold start it still has a rough idle and sometimes even shuts off after about 30seconds of so if i don't drive off within that time. IMO i think the new fuel pump symptoms are worse than my old one...at least with my old pump i never had it shut off on me at cold start.. BUT if i drive off immediately it's fine, no rough idle. With that being said, i was still wondering why it would be and realized i didn't check the voltage at the fuel pump when primed. It read 8.5 volts and my battery read 12v. I saw on youtube that it should be around 11v to 12v...does this mean that my relay should be the last culprit?